Project Summary/Abstract: Transplantation is a highly successful therapy for end-stage renal disease but there is a significant shortage of available donor organs that has forced utilization of low-quality kidneys to save patient?s lives. Extending the donor criteria has coincided with a growing appreciate that factors associated with organ donation, procurement and storage greatly affect post-transplantation outcomes. Unlike heart transplantation, kidney donors can be derived from a variety of sources that include living donors, donation after brain death, and donation after cardiac death. However, the vast majority of kidneys are donated from deceased donors and donation after brain death or after cardiac death predispose poorer post-transplantation outcomes. Problems inherent to organ transplantation, such as ischemia and extended cold storage, also negatively affect and cause irreparable damage to the donor kidney. These injurious events are known to elicit endothelial cell (EC) dysfunction, inflammation, and organ injury that are further exacerbated upon implantation by ischemia reperfusion injury (IRI) while also priming the donor organ for alloimmune recognition. While cold preservation has greatly facilitated the use of cadaveric kidneys for transplantation by slowing metabolism to prevent cell death, current formulations do not minimize organ injury associated with cold storage or ischemia reperfusion injury. Vascular endothelum, which serves as a dynamic interface between the allograft and the recipient, is the initial target of the deleterious events that adversely affect graft health and function. Since gap and tight junctions regulate EC functionality, therapeutic strategies that promote the molecular and cellular integrity of endothelium of donor kidneys could preclude the mechanisms responsible for allograft damage and failure. FirstString Research Inc. has identified, characterized, and clinically-evaluated a novel peptide mimetic of connexin43, alpha-Connexin Carboxy-Terminal (aCT1), that stabilizes the gap and tight junctions of ECs during wound healing processes, leading to coordination of cellular communication, dampened inflammatory responses, reduced immune cell infiltrate, and enhanced regenerative properties. aCT1?s small, stable, soluble design facilitates direct translocation into cells for intracellular drug delivery. Preliminary studies in clinically relevant models of kidney, heart, and lung transplantation reveal that aCT1 supplementation to standard-of-care organ preservation solutions stabilizes cellular junctions to protect EC from injurious effects of IRI and extending cold storage time. We hypothesize that cold preservation induces cell junction damage, which leads to EC dysfunction, inflammation, and renal damage upon reperfusion, and that supplementation of the therapeutic aCT1 peptide to standard of care preservation solution will preserve cell junctions, thereby improving renal health and function leading to superior post-transplantation outcomes. Here we propose to investigate the effect of ex vivo aCT1 pretreatment on donor kidney function, inflammatory state, and tissue injury using clinically relevant pig kidney transplantation models and low-quality human kidneys.